This invention comprises simple and inexpensive apparatus for closing a threaded opening in a container. The apparatus is particularly useful in conjunction with the filter described and claimed in my U.S. Pat. No. 4,626,347 (Dec. 2, 1986), the entire content of which is incorporated herein by reference. Briefly stated, U.S. Pat. No. 4,626,347 discloses filtration apparatus that attaches to an opening in a tank, especially an oil tank. A cable hangs from apparatus attached to an opening in the tank and a floating filter slides along the cable. The filter is connected to the outside of the tank by at least two partially flexible conduits that pass through the apparatus attached to the tank opening. The hole closure apparatus disclosed in my U.S. Pat. No. 4,626,347, while very effective, is constructed mostly of metal and has a relatively large thread that matches the threaded opening on the oil tank. The apparatus of the present invention is comprised mostly of flexible material, e.g. rubber, and requires, in the preferred embodiment, only one small thread. Hence the apparatus of the present invention is simpler and less expensive to produce.
A prior art closure for soft drink bottles having smooth necks uses a rubber plug, two disks abutting each end of the plug, and apparatus for causing the disks to move toward each other, thereby causing the rubber to expand and seal the smooth opening in the neck of the bottle. The present invention also uses two disks to compress a flexible plug. However, the resulting expansion of the flexible plug will not easily fill and seal the threads of the threaded opening. Fortunately the present invention overcomes this difficulty.